Membrane transport is essential to the functioning of a cell because it allows for substances, such as ions and chemicals, to pass membrane barriers. Remember that membranes are selectively permeable, meaning that some substances are able to pass freely while others cannot.

Biological membranes are both hydrophobic and hydrophilic in nature. Thus they are amphiphilic molecules. Cell membranes are organized in bilayers, with their hydrophobic tails facing inwards and their hydrophilic heads facing outwards. This specific arrangement means that small, nonpolar molecules can freely cross the membrane. Conversely, large polar molecules such as sugars and charged ions cannot freely pass.

There are two basic types of membrane transport:

Passive Diffusion: This is a type of transport which follows a concentration gradient. The flow of particles is from a high concentration area to a low concentration area and requires no energy input. In addition, this process depends on the characteristics of the substance requiring transport such as its size, charge and hydrophobicity. For example, nonpolar molecules and small polar molecules can move freely with a concentration gradient. Furthermore, passive diffusion includes osmosis, which describes the movement of water across a membrane and facilitated diffusion, which uses channel proteins or carrier proteins to transport particles.

Active Transport: This is a type of transport which requires energy because molecules are pumped against a concentration gradient. There is both primary active transport, which directly uses ATP from a pump, and secondary active transport which does not directly utilize ATP, but rather an electrochemical gradient. Carrier proteins, such as antiporters and symporters are used in secondary active transport. Endocytosis and exocytosis are two types of transport requiring energy. Endocytosis brings particles into a cell, while exocytosis takes particles out of a cell.

All cells are surrounded by a phospholipid bilayer membrane. The function of the phospholipid bilayer is to act as a barrier between the living cell and the environment. The phospholipid bilayer also regulate the passage of solutes into and out of the cell. The phospholipid bilayer membrane can differentiate which solutes to mov

Begin by distinguishing between osmosis and diffusion; how are they similar? In what ways are they different?
What properties of the cell membrane do they utilize to transport substances across the cell membrane?
Let's end with definitions and explanations of membrane potentials.

1. As a person becomes very dehydrated, the concentration of water in her blood decreases. In which direction will water move across the plasma membranes of her blood cells? What will happen to the volume of the cells as a consequence? Why is proper hydration important for multicellular organisms?
2. Oops! You were cleaning

1. Several ions are responsible for the resting membrane potential. Describe the forces that determine resting membrane potential.
2. How are graded potentials created, and how are they different from action potentials?
3. Discuss the ion channels that are involved in the generation of an action potential.
4. Descri

Please provide some information about the relationships between the intra -cellular compartments involved in the secretory and endocytic pathways, also please distinguish between co-translational and post translational protein targeting.

Can you help me with the following question in at least 300 words?
Is the production of water by the electron transport chain catalyzed by cytochrome oxidase, ubiquinone, cytochrome c, cytochrome b or complex I?

If you put a 2% sucrose solution on one side of a selectively permeable membrane and a 7% surcose solution on the other side, the side with the 2% solution is _____ to the side with the 7% solution:
a. hypotonic
b. hypertoinc
c. isotonic

1) Would the passive movements of substances occur if the interstitial solute concentration was the same as the filtrate solute concentration?
2) Matching:
1.) Causes production of dilute urine
2.) results in increased sodium loss.
3.) Causes the body to retain more Potassium.
4.) Will cause water retention due to sodiu

The addition of oligomycin to mitochrondria markedly drecreased both the rate of electron transfer from NADH to oxygen and the rate of ATP formation. The susbequent addition of DNP leads to an increase in the rate of electron transfer without changing the rate of ATP formation. What does oligomycin inhibit and what is the mech

2. Give a functional definition of a eukaryotic gene. Please include all parts of a eukaryotic gene and what the function of each element is. Which parts of a newly synthesized eukaryotic mRNA molecule do not transmit information for the synthesis of protein? Why?
3. What is the difference between a lytic and a lysogenic

During an experiment a neuropsychologist measures the membrane potential of a squid giant axon in the presence of a bathing solution of known composition. He then removes the cytoplasm and replaces it with a synthetic solution. At the same time he alters the external medium from that used before and again measures the membrane

Problem:
(a) In skeletal muscle the Ca+2 concentration is controlled by the SR (sarcoplasmic reticulum). At rest, the Ca+2 pump of the SR can maintain a concentration gradient of 0.5 mM inside SR / 0.1 µM cytoplasm (aka, outside the SR). How much energy is stored in this gradient; ignore the effects of charge.
(b) The p

NEED A HYPOTHESIS FOR EACH OF THE THREE ITEMS BELOW:
Hypothesis for the Elodea Plant Cells:
1.
2.
3.
Conclusion for each:
1. Elodea Plant Cells in
Distilled Water at 400x
Conclusion is .... ????
2. Elodea Plant Cells in
Pond Water at 400x
Conclusion is .... ????
3. Elodea Plant Cells in
Sa

Lab5A
Procedure
The molecules of all matter, particularly gases and liquids, are in constant vibration motion. As a result of this motion, molecules are continually colliding with one another, much like balls scattering over a pool table. Using a microscope, you can observe these molecular collisions that produce the effects o

Active transport is the
A) diffusion of molecules within a cell
B) movement of molecules into or out of a cell against a concentration gradient
C) movement of molecules into or out of a cell down a concentration gradient
D) movement of molecules into or out of a cell using special proteins and not requiring an

What sorts of member molecules may be distributed asymmetrically? Why does it make sense for certain components of membranes to be asymmetrically distributed? Give specific examples. How can a membrane maintain asymmetry despite its fluid consistency?

The difference in pH between the internal and external surfaces of the inner mitochondrial membrane is 1.4 pH units (external side acidic). If the membrane potential is assumed to be 0.06 V (inside negative) what is the free energy released upon transporting 1 mol of protons back across the membrane? How many protons must be tr

I need a basic explanation of the difference in the rates at which glucose is transported across a cell membrane versus the concentration gradient of glucose. I am trying to understand the difference in diffusion through a lipid bilayer compared to facilitated diffusion. I could also really use help with finding online referen

Synaptic Vesicles are (Choose all that Apply)
Are contained within the postsynaptic cell cytoplasm
Fuse with the presynaptic membrane in response to increased intracellular calcium concentration
House the neurtransmitters that will ultimately be released into the synaptic cleft in response to an action potential arr